Various thermal destruction processes for disposing of hazardous wastes are known in the art. There are two general types of thermal destruction processes, incineration systems and high efficiency boilers. An attempt has been made to use each of these systems for the destruction of various hazardous wastes, including PCBs.
One type of incinerating system known in the prior art is the rotary kiln incinerator. The rotary kiln incinerator is a cylindrical-refractory lined shell that is mounted horizontally at a slight incline. Waste is fed into the upper end and fuel is fed at the lower end of the kiln. Air is provided for combustion with the fuel to produce heated combustion air. The rotation of the shell causes mixing of the waste with the combustion air and provides sufficient turbulence and agitation to oxidize the waste. It is sometimes necessary to install a secondary high temperature combustion chamber to complete the destruction of vapor phase and particulate materials. The rotary kiln exhibits several problems including the possibility of poor sealing of the rotary kiln ends causing possible leakage of the hazardous waste material. Also, the rotary kiln type of incinerator is relatively expensive, has a low thermal efficiency, and particulate emission is difficult to control.
A second type of incinerator known in the prior art is a liquid injection type incinerator which may be used to dispose of virtually any liquid which is combustible and has a viscosity which allows pumping. The liquid injection type of incinerator also exhibits several problems. The hazardous waste must be presented to the system in the form of a liquid having a viscosity low enough to be pumped and to be atomized in a burner. The burners are subject to plugging, erosion, and corrosion from the fluid presented. Also, the maintenance of combustion efficiency requires sophisticated instrumentation with its attendant expenses.
In the above-mentioned wet oxidation systems, organic wastes are catalytically oxidized with air presented as a aqueous solution in a high pressure environment. In wet oxidation systems, the PCB waste must be in dilute aqueous solution. Also, it has been heretofore impossible to produce the high destruction efficiencies necessary for disposal of extremely hazardous chemicals such as PCBs with this method. Here, the high pressure operation is difficult to control and thus requires special designs and safety measures which may be extremely expensive to implement.
Recently, the Environmental Protection Agency has promulgated a body of regulations termed the Resource Conservation and Recovery Act. This Act places severe restrictions on the producers of hazardous wastes and under a "cradle-to-grave" liability clause and forces producers to be involved in the storage and disposal of their wastes.
The present invention, while useful for incinerating a variety of organic hazardous wastes, is particularly adapted for the incineration of polychlorinated biphenyl (PCB). PCBs have been used extensively in the manufacturing of electrical power transformers. PCB is a stable organic compound of low vapor pressure and dielectric which is extremely resistent to oxidation and is immiscible in water. While these properties make PCB a good electrical transformer fluid, they also make it extremely difficult to break down the chemical. PCB which enters the natural environment will remain in its stable form for years and remain a hazard to human health. Thus, PCB has been determined by the Environmental Protection Agency to be hazardous waste and it is thus subject to close control. Presently, the EPA requires 99,9999 percentage destruction of PCBs.
At the present time, the most attractive process for destroying PCB is the use of high temperature oxidation in which the PCB is converted into its oxide elements. Normally, the aforementioned rotary kiln combustion device is used. The rotary kiln provides an insulated combustion chamber having a relatively low velocity and high residence time of the hazardous material. Thus, a relatively large rotary kiln displays only relatively low mass throughout characteristics. In the rotary kiln, a high residence time is necessary at the normal operating temperature of 1200.degree. C. with 3 percent excess oxygen. It is apparent that incineration of PCBs using a rotary kiln is far from the optimum process.
Heretofore, high mass flux oxygen blown combustors have not been applied to the problem of hazardous waste incineration for commercial applications. The present invention utilizes high mass flux oxygen blown combustion in order to solve many of the problems attendant in the prior art systems.